Deaths Prompt Call for Pet Rodent Suppliers to Screen for Virus

A case involving seven transplant recipients killed by a rodent-borne virus that they apparently acquired from donated and infected human organs has prompted a recommendation that regulatory authorities require suppliers of pet rodents to screen their colonies for the virus.

According to two articles in the May 25, 2006, issue of the New England Journal of Medicine, seven out of eight infected transplant recipients died from lymphocytic choriomeningitis virus (LCMV) that they almost indisputably received with donated organs. The organs came from two donors, both of whom died from unrelated causes but were silently infected with LCMV. One donor had acquired the virus from a pet hamster and the other from unknown sources, but neither showed outward signs of the disease, the articles said.

LCVM was “among the first human pathogenic viruses to be isolated” by medical researchers in the mid-1930s. It is one of about 20 members of the virus family Arenaviridae, each one of which in nature infects a separate rodent species that spreads the virus but causes minimal or no overt disease in the rodent host, according to Dr. C.J. Peters, professor of pathology and microbiology and immunology at the University of Texas Medical Branch at Galveston UTMB) and director for biodefense at UTMB’s Center for Biodefense and Emerging Infectious Diseases.

Most human infections with LCMV result in a mild to moderate viral meningitis, but in immuno-suppressed patients such as those receiving kidney transplants it causes a severe disease that resembles a related arenavirus disease from Africa called Lassa fever. Thousands of cases of Lassa fever occur every year in West Africa, and about 15 percent of them are fatal. The sole surviving transplant patient discussed in the NEJM articles was treated with the antiviral drug ribavirin, which has been shown to be effective against Lassa fever.

“One obvious way to reduce the risk of human infection with LCMV is to have suppliers of pet rodents screen their colonies for the infection,” Peters writes in the journal article titled “Lymphocytic Choriomeningitis Virus—Any Old Enemy up to New Tricks.” He notes that mice are known to carry LCMV infection that they can spread to other species without getting sick themselves. Hamsters and possibly other pet rodents, although not natural hosts in the wild, can be infected and transmit the virus in breeding colonies “with disastrous consequences,” Peters notes.

“Wild mice can introduce LCMV into colonies of either hamsters or mice,” Peters’ article continues. “Thus, regulations to ensure the absence of virus in rodent colonies would reduce the risk of LCMV infection posed to pet owners and decrease the risk of transmission from transplanted organs.

“Such screening seems justified,” the paper continues, “given the serious nature of LCMV disease and the particular risk to fetuses: LCMV infection in pregnant women is an increasingly recognized cause” of the birth defects “hydrocephalus, mental retardation, and chorioretinitis in newborns.”